With Xcode 4.2 and the LLVM compiler, when compiling for ARMv6 there are some very weird bugs in the generated application (such as "width" property of CGSize returning the "height" instead). To fix this, I found I must set the compiler flag -mno-thumb. I know how to set compiler flags on a file-by-file basis, but is there a way to set a compiler flag for the entire project?
You can set project wide compiler flags in the project settings under the "Language" section of the "Build Settings" tab.